A new dinuclear cobalt complex selectively catalyses 4e− reduction of O2 to water in methanol containing acetic acid. Its TOF of 0.031 s−1 and overpotential of 690 mV outperform the few previous Co N,O-chelate based catalysts for the 4e− ORR. Replacing acetic acid with NH4PF6 as proton source induces a complete and unprecedented switch to the H2O2 producing 2e− pathway. Mechanistic studies suggest a peroxo intermediate for both pathways, with acetate coordination/decoordination determining the destination of a key electron transfer.